1. Field of the Invention
The present invention is directed toward an evaporative emission canister purge actuation monitoring system for a motor vehicle having a vapor canister, an engine, and at least one control unit.
2. Description of the Related Art
Automotive vehicles include fuel delivery systems having a fuel tank and fuel delivery lines. The fuel delivery lines typically include a plurality of conduits and associated connections operatively interconnecting the fuel tank with an internal combustion engine. A fuel pump is used to deliver the fuel under pressure from the tank to the engine via the fuel delivery lines. Many automotive vehicles are powered using gasoline as fuel. Gasoline is a volatile substance that generates gasses that, if untreated, are harmful to the environment. These gasses are generally referred to as evaporative emissions. Because they are gasses, these emissions can escape from the fuel system even through very small orifices that may present themselves throughout the fuel delivery system. Accordingly, various governmental authorities in countries throughout the world have long mandated that automotive vehicles include systems for preventing the release into the atmosphere of untreated or un-combusted fuel vapor generated in the fuel delivery system.
Thus, gasoline powered automotive vehicles typically include evaporative emission control systems that are designed to effectively deal with the evaporative emissions. Such systems typically include a vapor canister operatively connected in fluid communication with the fuel tank and the intake of the internal combustion engine. The vapor canister typically includes carbon or some other absorbent material that acts to trap the volatile evaporative emissions generated by the fuel system. A canister purge valve controls the flow of evaporative emissions between the canister and the intake of the engine. In turn, the operation of the canister purge valve is typically controlled by an onboard computer, such as the engine control module, or the like. During normal vehicle operation, and subject to predetermined operational characteristics, the canister purge valve is opened to subject the vapor canister to the negative pressure of the engine intake manifold. This purges the vapor canister of trapped gaseous emissions, effectively regenerating the canister so that it may absorb additional vapor.
During vehicle shutdown, the canister purge valve is closed and the evaporative emissions generated in the fuel system are routed from the fuel tank to the vapor canister where they are absorbed and stored for later purging as described above. During vehicle shutdown, the fuel system is effectively sealed from the ambient environment.
In addition to conventional evaporative emission control systems as described above, many governmental authorities have further mandated that these systems have self-diagnostic capabilities to determine if any leaks are present in the closed fuel system. As public concern over pollution has risen, some governmental authorities have promulgated tougher standards for automotive evaporative emission control systems. For example, the California Air Resource Board (CARB) now requires evaporative emission systems to detect leaks as small as 0.020 inches in diameter. Many of these systems employ sensors adapted to detect the presence of a vacuum that is naturally generated in the emission space of the fuel tank after shutdown and after the fuel system has cooled. Other known evaporative emission systems employ positive or negative pressure generated by some related system to test the sealed integrity of the fuel system.
While on-board diagnostic evaporative emission systems of the type proposed in the related art have generally worked for their intended purposes they have also suffered from the disadvantage of being relatively complex and costly. They also generally consist of a number of components which must be separately controlled and interconnected via flexible or hard conduits sometimes referred to as “on-board plumbing”. In many of the systems presently employed in the related art, each component often requires its own mounting strategy and associated fasteners. The on-board plumbing must be routed so as not to clutter the engine. This objective is not always met in evaporative emission systems known in the related art and they can be expensive to service. Further, and because of the ever-shrinking space available for the vehicle power plant, the effective use of space through efficient component packing is a parameter which designers must constantly seek to improve.
Thus, there remains a need in the art for an evaporative emission system which reduces the number of components needed to effectively monitor the system. Further, there is a need for such a system that reduces the complicated on-board plumbing of the type required for systems known in the related art. There is also a need in the art for an evaporative emission canister purge actuation monitoring system that is inexpensive to manufacture and easy to service in the field. Finally, there is a need in the art for an evaporative emission canister purge actuation monitoring system that has improved response time and accurate repeatability and that is smaller than present systems employed in the related art.